The present invention relates to an improvement in battery cell monitors in which the reduction of the level of the electrolyte of a wet cell battery below a predetermined level may be detected.
It has long been recognized that evaporation of electrolyte from wet cell atteries is a serious problem that can lead to reduced electrical power output and damage to the cells. Numerous devices have been proposed for monitoring the electrolyte level in, a battery cell. In one such device, a monitor monitors the electrolyte fluid level of individual battery cells on battery powered mobile or stationary equipment. The one piece monitor includes a probe housing with associated circuitry and two wire leads. The monitor wire lends may be permanently or temporarily attached to the battery system voltage and battery system ground. After removing the battery fill cap of a specific cell, the probe is inserted into the fill cap opening on the battery. The monitor""s electrolyte level indicator provides an indication that the, electrolyte is at the battery manufacturer""s recommended level. If the indicator does not illuminate, water needs to be added to the batteries. However, this device is not mounted in the cell opening, which is desirable for certain installations, and does not discriminate between the indicator not illuminating because the water is low or the indicator is not working.
The primary purpose of the present invention is to detect the level of electrolyte in a lead acid battery cell. It does so by placing a metal rod in the electrolyte solution, with the rod projecting into the battery cell to the minimum desired depth of electrolyte. While in contact with the electrolyte, current is caused to flow through the rod. When the electrolyte drops below the predetermined level, the contact between the rod and the electrolyte is lost and the current ceases to flow.
In actual practice contact is never really lost because a film of electrolyte is present on all interior surfaces of a battery cell. The film of electrolyte provides a conductive path that simulates contact with the electrolyte bath and produces false readings of electrolyte levels.
The present invention concerns an apparatus for detecting a reduction of a level of electrolyte in a wet cell battery comprising: an electrically conductive sensing rod adapted to be disposed within a cell of a battery in contact with an electrolyte in the cell; a voltage comparator means having an input connected to the rod and having output, the voltage comparator means generating a first output signal when a voltage at the input is greater than a reference voltage and generating a second output signal when a voltage at the input is less than the reference voltage; an indicator means being responsive to the first output signal for generating a green color visual signal and being responsive to the second output signal for generating a red color visual signal; and an audio alarm device connected to the output of the voltage comparator means and being responsive to the second output signal for generating an audio indication whereby when the rod is immersed in the electrolyte, the first visual signal is generated and when the rod is not immersed in the electrolyte, the second visual signal and the audio indication are generated.
The apparatus according to the present invention also can include a sensing means connected between the voltage comparator means and a pair of battery voltage input terminals, the sensing means selectively connecting the terminals to the voltage comparator means when a voltage of a battery connected to the input terminals exceeds a predetermined voltage level, wherein the predetermined voltage level is above a normal operating voltage of the battery and is below a charging voltage generated when the battery is connected to a battery charger.